Check Valve and Diaphram Pump

ABSTRACT

[Problem] To provide a check valve and a diaphragm pump employing the same which has a good response, and in which a valve chamber can be made small so as to be hardly influenced by bubbles.  
     [Means for Solution] A check valve includes a valve chamber  11  which is defined by a top wall  8  having an introducing port  8   a  of a fluid, a bottom wall  9  having an exhaust port  9   a  of the fluid, and a side wall, and a valve body  12   a  which is supported in the valve chamber  11  in a cantilever manner having its base end fixed to the side wall and its distal end formed as a free end, the valve body being arranged above the introducing port  8   a . The bottom wall  9  is formed with a valve seat  9   b  having an inclined face  9   b   2  which is inclined so as to be gradually separated from the top wall  8  along the valve body  12   a  from the base end toward the distal end thereof. When the valve body  12   a  in the cantilever shape moves between the top wall  8  and the valve seat  9   b , the valve body  12   a  is restricted by the valve seat  9  having the inclined face  9   b   2 , at opening and closing operation of the valve body  12   a , whereby a moving amount of the valve body  12   a  becomes smaller, and response time from an open state to a closed state becomes shorter.

TECHNICAL FIELD

The present invention relates to a check valve which is suitable for use in a pump for controlling a flow of liquid in a small amount, and a diaphragm pump employing the same.

BACKGROUND ART

Recently, in fields of fuel cells, medical care, analysis and so on, various pumps for controlling a flow of liquid in a small amount with high accuracy have been developed.

Conventionally, a check vale for a piezoelectric vibrator pump which has a piezoelectric vibrator as a drive source and a valve body in a cantilever shape formed in a frame part (a valve box, a valve chamber) has been proposed, for example, in Patent Document 1. This check valve includes a supporting arm, of which one end is inserted into an inner wall of the frame part to support the check valve, and the other end forms a valve body capable of closing a valve hole. The valve body and the supporting arm are made of metal, plastic or the like into an integral plate body.

Patent Document 1: JP-A-4-72479 (the right column of page 4, FIG. 1)

DISCLOSURE OF THE INVENTION Problems that the Invention is to Solve

The following problems remain in the above described conventional art.

Heretofore, metal, resin material, and rubber material have been used as material for the valve body in the cantilever shape. This valve body can be opened with pressure. However, because the valve body has rigidity, an amount of its deformation is not stable due to variation of components and assembling, and there has been such inconvenience that times when the valve is closed are not stable, and hence, response is also unstable.

In case where the valve body is made of resin material, the valve body has a thickness to some extent, and a considerable force is required to deform the valve body into an open state. Under the circumstances, it is possible to minimize the required force by increasing a longitudinal length of the valve body, which however, incurs an increase in size (capacity) of the valve chamber, and an increase of a residence space of bubbles which is generated by vaporization of gas dissolved in the liquid. Consequently, liquid conveying ability of the pump is influenced, and plastic deformation of the valve body is also concerned.

When the valve body is made of rubber material, plastic deformation is not concerned. However, there is a limit in reducing the thickness of the valve body, and there are substantially same inconveniences as that made of resin material in respect of the force required for deformation and the size.

The invention has been made in view of the above described problems, and it is an object of the invention to provide a check valve and a diaphragm pump employing the same which has a good response, and in which a valve chamber can be made small so as to be hardly influenced by bubbles.

MEANS FOR SOLVING THE PROBLEMS

In order to solve the above described problem, the invention has adopted the following structure. Specifically, a check valve according to the invention includes a valve chamber which is defined by a top wall having an introducing port of a fluid, a bottom wall having an exhaust port of the fluid, and a side wall, and a valve body which is supported in the valve chamber in a cantilever manner having its base end fixed to the side wall and its distal end as a free end, the valve body being arranged above the introducing port, and characterized in that the bottom wall includes a valve seat having an inclined face which is inclined so as to be gradually separated from the top wall along the valve body from the base end to the distal end of the valve body.

In this check valve, the valve seat having the inclined face is formed on the bottom wall. Therefore, when the valve body in the cantilever shape moves between the top wall and the valve seat having the inclined face, the valve body is restricted by the valve seat having the inclined face at the opening and closing operation of the valve body, whereby a moving amount of the valve body becomes smaller, and response time from an open state to a closed state becomes shorter. Moreover, because the moving amount has been restricted to be smaller, the valve chamber can be made small, and is not be easily influenced by bubbles. Further, even though the soft valve body made of flexible material is used, deformation of the valve body is unlikely to occur because the valve body is restricted by the inclined face of the valve seat.

Moreover, the check valve according to the invention is characterized in that the valve seat includes a groove of which one end is connected to the exhaust port and the other end extends beyond the distal end of the valve body. Specifically, according to this check valve, because the groove is formed in the valve seat, the fluid is able to flow out from the other end of the groove which is arranged at the distal end side of the valve body to the exhaust port through the groove, even though the valve body is arranged above the exhaust port in contact with the inclined face of the valve seat, when the valve body is pushed by the fluid into an open state.

Moreover, the check valve according to the invention is characterized in that at least one of the introducing port and the exhaust port is disposed at a side of the base end of the valve body. When the introducing port and the exhaust port are arranged at the distal end side of the valve body, there is such anxiety that a strong force may be exerted on the distal end of the valve body to deform the valve body, in some cases. However, in the check valve according to the invention, at least one of the introducing port and the exhaust port is disposed at the base end side of the valve body, and therefore, the strong force is not be exerted on the distal end side of the valve body. Accordingly, deformation of the valve body is restricted, and hence, normal opening and closing operation of the valve can be maintained. Particularly, when the valve seat having the above described groove is employed, even in case the exhaust port is disposed at the base end side of the valve body, passage of the fluid can be ensured by the groove, and favorable valve operation can be maintained.

Further, the check valve according to the invention is characterized in that the valve body is made of a flexible film. Specifically, because the soft and thin valve body made of the flexible film is used in this check valve, the valve body has least rigidity, and the force required for deformation is small. Accordingly, it is possible to shorten the longitudinal length of the valve body, and to reduce volume of the fluid required for the opening and closing operation. As the results, the valve chamber can be made smaller in size, and hence, response and stability of the valve operation is enhanced. At the same time, influence of bubbles can be further decreased.

Still further, the check valve according to the invention is characterized in that the check valve includes a first case body having the top wall, a second case body having the bottom wall, a film body having the valve body and sandwiched between the first case body and the second case body, the first case body being provided with a convex part, the second case body being provided with a concave part to be engaged with the convex part, and the convex part and the concave part are respectively formed with opposed faces which are parallel to each other and configured to sandwich the base end of the valve body therebetween. Because the base end of the valve body is sandwiched between the convex part and the concave part, the base end (a supporting point) of the valve body is defined. Accordingly, the valve body is positioned, and positional displacement of the valve body can be prevented. Moreover, because the valve body is sandwiched between the opposed faces which are formed in the convex part and the concave part, and parallel to each other, an angle of the valve body protruding into the valve chamber can be made constant, even in case where positional displacement between the convex part and the concave part may occur.

A diaphragm pump according to the invention includes: a diaphragm including a piezoelectric element attached thereto; an upper case body which defines a pressure room in cooperation with the diaphragm therebetween and has an upper intake flow passage and an upper discharge flow passage which are connected to the pressure room; a lower case body having a lower intake flow passage which is connected to the upper intake flow passage through an intake side check valve and a lower discharge flow passage which is connected to the upper discharge flow passage through a discharge side check valve, and is characterized in that each of the intake side check valve and the discharge side check valve is the check valve according to the above-described invention, the exhaust ports are respectively connected to the upper intake flow passage and the lower discharge flow passage, the introducing ports are respectively connected to the upper discharge flow passage and the lower intake flow passage.

Specifically, because the check valve according to the invention is employed as the intake side check valve and the discharge side check valve, this diaphragm pump has high response, and is hardly influenced by bubbles. As the results, a flow of liquid in a small amount can be controlled with high accuracy in this diaphragm pump.

ADVANTAGE OF THE INVENTION

According to the invention, the following advantages are obtained.

Specifically, according to the check valve of the invention, because the valve seat having the inclined face is formed on the bottom wall, the valve body is restricted by the valve seat having the inclined face, whereby a moving amount of the valve body becomes smaller. Therefore, high response can be obtained, and efficient and highly accurate valve operation is made possible. Moreover, because the valve chamber can be made small and is not easily influenced by bubbles, and at the same time, the valve body can be restricted by the inclined face of the valve seat, deformation of the valve body hardly occurs, so that highly accurate operation can be performed. Accordingly, by employing this check valve in the diaphragm pump, it is possible to control the flow of liquid in a small amount with high response and high accuracy, and it is possible to obtain a pump which is favorable for a fuel cell or the like.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, an embodiment of the check valve and the diaphragm pump employing the same according to the invention will be described, referring to FIGS. 1 to 5.

The diaphragm pump employing the check valve in this embodiment is a pump for a fuel cell for supplying methanol for example, as the fluid. As shown in FIG. 1, the diaphragm pump includes a diaphragm 2 to which a piezoelectric element 1 is attached, an upper case body 4 having an upper intake passage 4 a and an upper discharge passage 4 b which are communicated with a pressure room 3 formed between the upper case body 4 and the diaphragm 2, and a lower case body 6 having a lower intake passage 6 a communicated with the upper intake passage 4 a through an intake side check valve 5A and a lower discharge passage 6 b communicated with the upper discharge passage 4 b through a discharge side check valve 5B.

The diaphragm 2 includes a resin diaphragm 2 a, a part of a lower face thereof forming a wall of the pressure room 3, a metal diaphragm 2 b bonded on the resin diaphragm 2 a, and the piezoelectric element 1 bonded on the metal diaphragm 2 b. The piezoelectric element 1 which is a piezoelectric element (PZT) is connected to a power supply which is not shown, and expanded or contracted by application of electric voltage.

As shown in FIGS. 2 to 5, each of the intake side check valve 5A and the discharge side check valve 5B has a valve chamber 11 which is defined by a top wall 8 having an introducing port 8 a of the fluid, a bottom wall having an exhaust port 9 a of the fluid, and a side wall 10. A valve body 12 a is supported by the valve chamber 11 in a cantilever shape so that the base end is fixed to the side wall 10 and the distal end is a free end, and disposed above the introducing port 8 a.

In the intake side check valve 5A, the bottom wall 9 is formed on a lower face of the upper case body (a second case body) 4, and the top wall 8 is formed on an upper face of the lower case body (a first case body) 6. On the other hand, in the discharge side check valve 5B, the top wall 8 is formed on a lower face of the upper case body (the first case body) 4, and the bottom wall 9 is formed on an upper face of the lower case body (the second case body) 6.

Specifically, the exhaust ports 9 a are respectively connected to the upper intake flow passage 4 a and the lower discharge flow passage 6 b, while the introducing ports 8 a are respectively connected to the upper discharge flow passage 4 b and the lower intake flow passage 6 a.

The lower intake flow passage 6 a is connected to a supply source (not shown) of the fluid through a fluid supply pipe 13. The lower discharge flow passage 6 b is connected to a supplying destination (not shown) of the fluid through a fluid discharge pipe 14.

The valve body 12 a is formed in a tongue-like cantilever shape by stamping out a film body 12 which is interposed between the upper case body 4 and the lower case body 6. The film body 12 and the valve body 12 a are made of a flexible film such as PP (polypropylene). The upper case body 4 and the lower case body 6 are bonded to each other having the film body 12 interposed therebetween, by laser welding in a hatched region R as shown in FIG. 3. In FIGS. 4 and 5, the valve body 12 a is shown in a state incorporated between the upper case body 4 and the lower case body 6. The valve body 12 a in this embodiment is not subjected to embossing work or so, but formed in a shape of a flat plate, as shown in FIG. 2(b).

The bottom wall 9 is provided with a valve seat 9 b including a flat face 9 b 1 which is substantially parallel to the top wall 8 with a space in a state opposed to the top wall 8, and an inclined face 9 b 2 which is continued from the flat face 9 b 1 and inclined along the valve body 12 a so as to be gradually separated from the top wall 8 from the base end toward the distal end.

The inclined face 9 b 2 of the valve seat 9 b includes a groove 9 c. One end of the groove 9 c is connected to the exhaust port 9 a and the other end is extended beyond a distal end of the valve body 12 a. It should be noted that the valve seat 9 b is larger than the valve body 12 a both in a lateral direction and in a longitudinal direction so that a whole body of the valve body 12 a can be supported.

The introducing port 8 a and the exhaust port 9 a are arranged at a base end side of the valve body 12 a, and opposed faces P2 formed in a lower concave part 16 b and an upper concave part 17 a, which will be described below, are continuously provided from the flat face 9 b 1.

On the lower face of the upper case body 4, there are formed an upper convex part 16 a in a V-shape in cross section at a side of the discharge side check valve 5B, and an upper concave part 17 a in an inverted V-shape in cross section at a side of the intake side check valve 5A. On the other hand, on an upper face of the lower case body 6, there are formed the lower concave part 16 b in a V-shape in cross section to be engaged with the upper convex part 16 a which is arranged at the side of the discharge side check valve 5B, and the lower convex part 17 b in an inverted V-shape in cross section to be engaged with the upper concave part 17 a which is formed at the side of the intake side check valve 5A.

The upper convex part 16 a, the lower concave part 16 b, the upper concave part 17 a, and the lower convex part 17 b are provided so as to extend wider than the valve body 12 a in a direction perpendicular to the longitudinal direction of the valve body 12 a.

The upper convex part 16 a and the lower concave part 16 b to be engaged with each other are respectively provided with opposed faces P1, P2 which are parallel to each other and adapted to sandwich the base end of the valve body 12 a therebetween. In the same manner, the upper concave part 17 a and the lower convex part 17 b are respectively provided with opposed faces P1, P2 which are parallel to each other and adapted to sandwich the base end of the valve body 12 a therebetween. These opposed faces P1, P2 are inclined at a determined angle with respect to the bottom wall 8.

Because the base end of the valve body 12 a is sandwiched between the upper convex part 16 a and the lower concave part 16 b, or between the upper concave part 17 a and the lower convex part 17 b, the base end (a supporting point q) of the valve body 12 a is defined. Accordingly, the valve body 12 a is positioned, and positional displacement of the valve body 12 a can be prevented. Moreover, because the opposed faces P1, P2 are formed so as to be inclined at a determined angle with respect to the bottom wall 8, the valve body 12 a can be arranged in such a manner that the valve body 12 a may be pressed against the introducing port 8 a in a closed state. Further, because the valve body 12 a is supported in a cantilever shape, and sandwiched between the upper concave part and the lower convex part to define the supporting point, it is possible to maintain highly accurate valve operation, even though the valve body 12 a may be expanded or contracted due to swelling by methanol or temperature change.

Still further, because the valve body 12 a is sandwiched between the opposed faces P1, P2 which are formed in the upper convex part 16 a and the lower concave part 16 b and in the upper concave part 17 a and the lower convex part 17 b, and parallel to each other, an angle of the valve body 12 a protruding into the valve chamber 11 can be made constant, even when positional displacement between the upper convex part 16 a and the lower concave part 16 b or between the upper concave part 17 a and the lower convex part 17 b may occur. When the valve body 12 a is sandwiched between a concave part and a convex part which have respective curvatures, angles of faces sandwiching the base end of the valve body 12 a may vary, when displacement occurs between the concave part and the convex part at a time of engagement. For this reason, there has been such inconvenience that a manner of protrusion (a protruding angle) of the valve body 12 a into the valve chamber 11 may vary. However, in this embodiment, because the valve body 12 a is sandwiched between the parallel faces, the angles of the opposed faces P1, P2 which sandwich the base end of the valve body 12 a are constant, even in case where assembling displacement may occur. As the results, it is possible to obtain the valve body 12 a which protrudes into the valve chamber 11 at the determined angle, with high accuracy.

Now, operation of the diaphragm pump and the check valve will be described hereunder, referring to FIGS. 1 and 2.

Operation of the diaphragm pump as a whole will be first described. When an electric voltage is applied so that the piezoelectric element 1 may be expanded and contracted, a whole body of the diaphragm 2 makes bending movement in a manner of oscillating up and down, in association with the piezoelectric element 1.

When the fluid in the pressure room 3 is pressurized with the bending movement of the diaphragm 2, the fluid is discharged to the fluid discharge pipe 14 through the upper discharge flow passage 4 b, the discharge side check valve 5B, and the lower discharge flow passage 6 b. Meanwhile, in the intake side check valve 5A, the valve body 12 a closes the introducing port 8 a thereby to prevent a backflow of the fluid to the fluid supply pipe 13.

Then, when the pressure in the pressure room 3 is reduced with the bending movement of the diaphragm 2, the fluid is sucked into the pressure room 3 through the fluid supply pipe 13, the lower intake passage 6 a, the intake side check valve 5A, and the upper intake flow passage 4 a. Meanwhile, in the discharge side check valve 5B, the valve body 12 a closes the introducing port 8 a thereby to prevent a backflow of the fluid to the fluid discharge pipe 14. In other words, as the diaphragm 2 repeats the bending movements, the fluid can be forwarded through the intake side check valve 5A and the discharge side check valve 5B which prevent the backflow.

In each of the intake side check valve 5A and the discharge side check valve 5B, opening operation of the valve when the fluid flows into the valve chamber 11 is performed as follows.

When the fluid flows into the valve chamber 11 through the introducing port 8 a from the lower intake flow passage 6 a or the upper discharge flow passage 4 b, the valve body 12 a which has closed the introducing port 8 a is pushed up by the fluid. At this moment, the valve body 12 a is restricted by the valve seat 9 b having the inclined face 9 b 2 to be in a state where a certain flow path is ensured in the valve chamber 11. The fluid which has flowed into the valve chamber 11 flows from the base end side to the distal end side of the valve body 12 a, and flows into the groove 9 c from one end of the groove 9 c which is open toward the distal end side of the valve body 12 a. The fluid is further discharged from the exhaust port 9 a to the upper intake flow passage 4 a or the lower discharge flow passage 6 b through the groove 9 c.

Specifically, even while the valve body 12 a is in contact with the valve seat 9 b, the fluid is able to flow out to the exhaust port 9 a through the groove 9 c. Moreover, because the introducing port 8 a and the exhaust port 9 a are arranged at the base end side of the valve body 12 a, strong force of the fluid is not exerted on the distal end side of the valve body 12 a. Accordingly, deformation of the valve body 12 a is restricted, and hence, normal opening and closing operation of the valve can be maintained. It is possible to obtain the substantially same effect by arranging at least one of the introducing port 8 a and the exhaust port 9 a at the base end side of the valve body 12 a. Moreover, it should be noted that the above described effects can be obtained more efficiently, by arranging both the introducing port 8 a and the exhaust port 9 a at the base end side of the valve body 12 a.

To the contrary, when the fluid backflows from the exhaust port 9 a to flow into the valve chamber 11, the valve body 12 a which has been restricted by the valve seat 9 b returns to the original position and close the introducing port 8 a. In this manner, the closing operation will be performed and the backflow can be prevented.

As described above, in this embodiment, the valve seat 9 b having the inclined face 9 b 2 is formed on the bottom wall 9. Therefore, when the valve body 12 a in the cantilever shape moves between the top wall 8 and the valve seat 9 b, the valve body 12 a is restricted by the valve seat 9 b having the inclined face 9 b 2, at the opening and closing operations of the valve body 12 a, whereby a moving amount of the valve body 12 a becomes smaller, and response time from an open state to a closed state becomes shorter. Moreover, because the moving amount is restricted to be smaller, the valve chamber 11 can be made small, and is not easily influenced by bubbles. Further, even though the soft valve body 12 a of a flexible film is used, deformation of the valve body 12 a is unlikely to occur, because the valve body 12 a is restricted by the inclined face 9 b 2 of the valve seat 9 b. Still further, the valve seat 9 b is provided with the flat face 9 b 1 at the base end side of the valve body 12 a thereby to restrict movement of the base end (the supporting point q) of the valve body 12 a at the bending movement. As the results, excessive plastic deformation of the valve body 12 a due to excessive stress exerted on the base end (the supporting point q) is prevented. Although the flat face 9 b 1 is formed on the valve seat 9 b in this embodiment, it is also possible to form the inclined face 9 b 2 from the base end of the valve seat 9 b so as to be continued from the opposed face P2 between the lower concave part 16 b and the upper concave part 17 a, depending on the angle of the inclined face 9 b 2 or the material of the valve body 12 a.

Still further, the soft and thin valve body 12 a made of the flexible film has least rigidity, and the force required for deformation is small. Accordingly, it is possible to shorten the longitudinal length of the valve body 12 a, and volume of the fluid required for opening and closing the valve can be reduced. As the results, the valve chamber 11 can be made smaller in size, and hence, response and stability of the valve operation is enhanced. At the same time, influence of bubbles can be minimized.

Technical scope of the invention will not be limited to the above described embodiment, but various modifications can be added to the invention within a scope not deviated from the gist of the invention.

Although in this invention, the check valve and the diaphragm pump employing the same have been applied to the fuel supply pump for a fuel cell, it is possible to apply the invention to a check valve and a pump employing the same for another purpose. For example, the invention may be applied to a dilute water circulating pump for a fuel cell, a medical pump for controlling a flow of medicinal solution in a small amount, a pump for analysis, and so on.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a diaphragm pump in an embodiment according to the invention.

FIG. 2 is a sectional view and an exploded sectional view showing check valves in the embodiment according to the invention.

FIG. 3 is a plan view of the check valves showing parts including valve chambers and laser welding regions in a phantom manner in the embodiment according to the invention.

FIG. 4 is an exploded perspective view showing the check valves in the embodiment according to the invention.

FIG. 5 is an exploded perspective view showing an essential part of the check valve including the valve chamber in the embodiment according to the invention.

DESCRIPTION OF THE REFERENCE NUMERALS AND SIGNS

-   1 Piezoelectric element -   2 Diaphragm -   3 Pressure room -   4 Upper case body (first case body, second case body) -   4 a Upper intake flow passage -   4 b Upper discharge flow passage -   5A Intake side check valve -   5B Discharge side check valve -   6 Lower case body (first case body, second case body) -   6 a Lower intake flow passage -   6 b Lower discharge flow passage -   8 a Introducing port -   8 Top wall -   9 Bottom wall -   9 a Exhaust port -   9 b Valve seat -   9 c Groove -   10 Side wall -   11 Valve chamber -   12 Film body -   12 a Valve body -   16 a Upper convex part -   16 b Lower concave part -   17 a Upper concave part -   17 b Lower convex part 

1. A check valve comprising: a valve chamber which is defined by a top wall having an introducing port of a fluid, a bottom wall having an exhaust port of the fluid, and a side wall; and a valve body which is supported in the valve chamber in a cantilever manner, the valve body having a base end fixed to the side wall and a distal end as a free end, the valve body being arranged above the introducing port, wherein the bottom wall includes a valve seat having an inclined face which is inclined so as to be gradually separated from the top wall along the valve body from the base end to the distal end of the valve body, and wherein the exhaust port is disposed on the valve seat.
 2. The check valve according to claim 1, wherein the valve seat includes a groove of which one end is connected to the exhaust port and the other end extends beyond the distal end of the valve body.
 3. The check valve according to claim 1, wherein at least one of the introducing port and the exhaust port is disposed at a side of the base end of the valve body.
 4. The check valve according to claim 1, wherein the valve body is made of a flexible film.
 5. The check valve according to claim 1, further comprising: a first case body having the top wall; a second case body having the bottom wall; and a film body having the valve body and sandwiched between the first case body and the second case body, wherein the first case body includes a convex part, wherein the second case body includes a concave part to be engaged with the convex part, and wherein the convex part and the concave part are respectively formed with opposed faces which are parallel to each other and configured to sandwich the base end of the valve body therebetween.
 6. A diaphragm pump comprising: a diaphragm including a piezoelectric element attached thereto; an upper case body which defines a pressure room in cooperation with the diaphragm therebetween and has an upper intake flow passage and an upper discharge flow passage which are connected to the pressure room; and a lower case body including a lower intake flow passage which is connected to the upper intake flow passage through an intake side check valve, and a lower discharge flow passage which is connected to the upper discharge flow passage through a discharge side check valve, wherein each of the intake side check valve and the discharge side check valve is the check valve according to claim 1, the exhaust ports are respectively connected to the upper intake flow passage and the lower discharge flow passage, the introducing ports are respectively connected to the upper discharge flow passage and the lower intake flow passage.
 7. The check valve according to claim 2, wherein at least one of the introducing port and the exhaust port is disposed at a side of the base end of the valve body.
 8. The check valve according to claim 2, wherein the valve body is made of a flexible film.
 9. The check valve according to claim 2, further comprising: a first case body having the top wall; a second case body having the bottom wall; and a film body having the valve body and sandwiched between the first case body and the second case body, wherein the first case body includes a convex part, wherein the second case body includes a concave part to be engaged with the convex part, and wherein the convex part and the concave part are respectively formed with opposed faces which are parallel to each other and configured to sandwich the base end of the valve body therebetween. 